Increased sensitivity for fuze oscillators

ABSTRACT

1. In a Doppler-type ordnance proximity fuze, said fuze having a tank circuit and means for causing radio-frequency energy of frequency fo to circulate in said tank circuit, said fuze also having antenna means for radiating radio-frequency energy of frequency fo from said tank circuit and for receiving a returned portion of said energy after reflection from a target, said returned portion as received by said antenna means having the frequency fo + Delta f, the frequency shift Delta f being due to the relative motion of said fuze and said target, said returned portion having the effect of amplitude-modulating the radio-frequency energy in said tank circuit at a modulation frequency Delta f, said fuze also having rectifier means for the half-wave rectification of a portion of the thus-modulated radiofrequency signal in said tank circuit to obtain a rectified signal having a component of frequency Delta f, said fuze also having a detonator-firing circuit responsive to a component of frequency Delta f, the improvement comprising: a diode having its cathode connected to said rectifier means to receive said rectified signal; a resistance connected between the anode of said diode and ground; a capacitance across said resistance; said diode and said capacitance cooperating with said rectifier means to provide voltage doubling of said portion of the thus-modulated radio-frequency signal in said tank circuit; and means connected to the junction of said diode and said resistance for applying a signal of frequency Delta f to said detonator-firing circuit, the amplitude of the Delta f signal at said junction being approximately twice the amplitude of the Delta f signal at said rectifier means.

United States Patent 1 Redcay Mar. 25, 1975 INCREASED SENSITIVITY FOR FUZE OSCILLATORS [75] Inventor: Paul Wilson Redcay, Washington,

[73] Assignee: The United States of America as represented by the Secretary of the Army, Washington, DC

[22] Filed: Sept. 21, I955 [21] Appl. No.: 535,769

[52] US. Cl. 102/70.2 P [51] Int. Cl. F42c 13/04 {58] Field of Search 102/702, 70.2 P; 343/6.8;

[56] References Cited UNlTED STATES PATENTS 2.222.759 11/1940 Burnside 102/702 P OTHER PUBLICATIONS Huntoon et al., Electronics, Dec. 1945, pp. 98403.

Primary E.vaminerBenjamin A. Borchelt Assistant Examiner-C. T. Jordan Attorney, Agent, or Firm Nathan Edelberg; Robert P. Gibson; Saul Elbaum EXEMPLARY CLAIM 1. In a Doppler-type ordnance proximity fuze, said fuze having a tank circuit and means for causing radio-frequency energy of frequency f, to circulate in said tank circuit, said fuze also having antenna means for radiating radio-frequency energy of frequency f, from said tank circuit and for receiving a returned portion of said energy after reflection from a target, said returned portion as received by said antenna means having the frequency f, Af, the frequency shift Af being due to the relative motion of said fuze and said target, said returned portion having the effect of amplitude-modulating the radio-frequency energy in said tank circuit at a modulation frequency Af, said fuze also having rectifier means for the half-wave rectification of a portion of the thus-modulated radiofrequency signal in said tank circuit to obtain a rectitied signal having a component of frequency Af, said fuze also having a detonator-firing circuit responsive to a component of frequency Af, the improvement comprising: a diode having its cathode connected to said rectifier means to receive said rectified signal; a resistance connected between the anode of said diode and ground; a capacitance across said resistance; said diode and said capacitance cooperating with said rectifier means to provide voltage doubling of said portion of the thus-modulated radio-frequency signal in said tank circuit; and means connected to the junction of said diode and said resistance for applying a signal of frequency Af to said detonator-firing circuit the amplitude of the Af signal at said junction being approximately twice the amplitude of the Af signal at said rectifier means.

2 Claims, 1 Drawing Figure AMPLIFIER 46 I THYRATRON DETONATOR WARHEAD Pmmmmz 3.872.791

AMPLIFIER f----- 46 4 I 2 THYRATRON DETONATOR 48 I WARHEA D INVENTOR Paul Wilson Reaca y Y QM'JZM QMM M ATTORNEYS INCREASED SENSITIVITY FOR FUZE OSCILLATORS The invention described herein may be manufactured and used by or for the Government for governmental purposes without the payment to me of any royalty thereon.

This invention relates to ordnance fuzes of the proximity type and more particularly to fuzes of the Doppler type. The invention provides improved Dopplertype fuze circuits in which the amplitude of the firing signal is roughly twice as great as that provided by known Doppler-type fuze circuits.

A typical Doppler-type proximity fuze comprises a vacuum-tube oscillator adapted to generate radiofrequency energy and an antenna adapted to radiate a portion of this energy and to receive such of the radiated energy as may be returned to the antenna after reflection from a target. As the fuze approaches a target the amplitude of the returned signal increases, and because of the well-known Doppler effect resulting from the changing path length traveled by the returned signal the returned signal, as received at the antenna, is shifted slightly in frequency with respect to the signal generated by the oscillator and radiated by the antenna. The diode action of the grid and cathode of the oscillator tube gives rise to a difference-frequency signal at the grid. The difference-frequency signal is taken from the grid, applied to an amplifier, and thence applied to the grid of a thyratron. When the differencefrequency signal at the grid of the thyratron reaches a sufficient positive-going value, the thyratron fires and in turn causes firing of a detonator and a warhead.

The principal feature of my invention entails the interposition of a diode and a capacitor between the oscillator grid and the amplifier in the above-described arrangement so as to provide voltage doubler action. As will be further explained below, the result is that the Doppler signal applied to the amplifier has substantially twice amplitude of the Doppler signal at the amplifier grid. My invention provides this manifest advantage an effective doubling of the sensitivity of the fuze conveniently and at very low cost; in general, nothing more than a diode, a capacitor, and a resistor need be added to a conventional fuze circuit.

A principal object of my invention is to provide a convenient, practical, low-cost modification of Doppler-type ordnance fuzes whereby the sensitivity of the fuze is substantially increased.

Another object of the invention is to provide, for Doppler-type ordnance fuzes, a convenient, practical, low-cost modification whereby the amount of amplification required for the Doppler signal may be substantially reduced.

Other objects, aspects, uses, and advantages of the invention will become apparent from the following description and from the accompanying drawing.

The drawing is a schematic-and-block diagram of a Doppler-type ordnance proximity fuze in accordance with my invention.

in the drawing, a vacuum-tube 12 having a preferably filamentary cathode 13, a grid 14, and a plate 15 is connected in a conventional radio-frequency oscillator circuit of frequencyf having a tank circuit 17 comprising a tank coil 18 and a tank capacitor 19. An antenna 22 is coupled to tank circuit 17 and radiates energy of frequency f,,. A portion of the radiated energy strikes a target 23, and a portion of the energy striking target 23 is reflected by target 23 and returned to antenna 22 and coupled back to tank circuit 17. Assuming that the fuze-to-target distance is changing, the returned energy has a frequency f,,+Af, the frequency shift Af being due to the well-known Doppler effect. It can be shown, is well known, and will be understood, that a principal effect of the returned energy is to cause the amplitude of the radio-frequency energy in tank circuit 17 to vary at the rate Af.

The radio-frequency signal in tank 17 may be considered to be applied to a half-wave rectifier circuit consisting of (a) the diode comprising grid 14 and cathode 13, (b) a capacitance comprising capacitors 24 and 25 between grid 14 and ground, and (c) a load resistance comprising grid resistor 28 and radio-frequency choke 27 in series therewith. When the fuze is far distant from target 23 there is negligible Af modulation of the radiofrequency signal in tank circuit 17, and a steady negative dc voltage E is developed at grid 14. As the fuze approaches target 23 the percentage of amplitude modulation of frequency Af applied to the radio-frequency signal in tank circuit 17 increases. The rectified signal at grid 14 follows the modulation; in other words, an a-c component e A; of frequency Af and of increasing amplitude is superimposed on the rectified d-c grid voltage E Instead of amplifying the e signal taken from grid 14, which is usual, I connect the cathode 32 of a diode 31 to grid 14. A capacitor 36 and a load resistor 37 are connected in parallel between anode 33 of diode 3l and ground. It will be seen that diode 31 is conductive on negative-going excursions of the radio-frequency signal at grid 14, while the diode consisting of grid I4 and cathode I3 is conductive on positive-going excursions of the radio-frequency signal at grid 14. The di odes I4, 13 and 31 in combination with the capacitors 25 and 24, and the capacitor 36 thus form a voltage doubler circuit fed by the radio-frequency voltage of the portion of the coil 18 which is in series with capacitors 25 and 24. As a result of the voltage doubler action obtained, therefore, the rectified d-c voltage at anode 33, and also the superimposed Af voltage developed as the fuze approaches target 23, have substantially twice the amplitude of the corresponding voltages at grid 14.

Unwanted radio-frequency components of the signal at anode 33 are preferably substantially removed by a low-pass filter which may conveniently consist of a resistor 41 and a capacitor 42. After filtering, the Af signal is applied through a blocking capacitor 43 to an amplifier 44 and thence to a suitably biased thyratron 46. When the Af signal applied to thyratron 46 attains a sufficient positive-going value, thyratron 46 fires and causes in turn the firing of a detonator 47 and a warhead 48.

It will be apparent that the embodiments shown are only exemplary and that various modifications can be made in construction and arrangement within the scope of the invention as defined in the appended claims.

I claim:

1. In a Doppler-type ordnance proximity fuze, said fuze having a tank circuit and means for causing radiofrequency energy of frequency fD to circulate in said tank circuit, said fuze also having antenna means for radiating radio-frequency energy of frequency f, from said tank circuit and for receiving a returned portion of said energy after reflection from a target, said returned portion as received by said antenna means having the frequency f -l-Af, the frequency shift Afbeing due to the relative motion of said fuze and said target. said returned portion having the effect of amplitudemodulating the radio-frequency energy in said tank circuit at a modulation frequency Af, said fuze also having rectifier means for the half-wave rectification of a portion of the thus-modulated radio-frequency signal in said tank circuit to obtain a rectified signal having a component of frequency Af, said fuze also having a detonator-firing circuit responsive to a component of frequency Af, the improvement comprising: a diode having its cathode connected to said rectifier means to receive said rectified signal; a resistance connected between the anode of said diode and ground; a capacitance across said resistance; said diode and said capacitance cooperating with said rectifier means to provide voltage doubling of said portion of the thus-modulated radio-frequency signal in said tank circuit; and means connected to the junction of said diode and said resistance for applying a signal of frequency Af to said detonator-firing circuit, the amplitude of the Af signal at said junction being approximately twice the amplitude of the Af signal at said rectifier means.

2. In a Doppler-type ordnance proximity fuze. said fuze having a tank circuit and means comprising a vacuum tube for causing radio-frequency energy of frequencyf to circulate in said tank circuit. said vacuum tube having at least a plate and a grid and a cathode. said fuze also having antenna means for radiating radiofrequency energy of frequency f,, from said tank circuit and for receiving a returned portion of said energy after reflection from a target, said returned portion as received by said antenna means having the frequency 5 f,,+Af. the frequency shift Af being due to the relative motion of said fuze and said target, said returned portion having the effect of amplitude-modulating the radio-frequency signal in said tank circuit at a modulation frequency Af, a portion of the thus-modulated radio-frequency signal in said tank circuit being rectified by a circuit including the diode consisting of said grid and said cathode and a first capacitance to obtain at said grid 21 negative d-c voltage upon which is superimposed an a-c voltage of frequency Af, said fuze also having a detonator-firing circuit responsive to the frequency Af, the improvement comprising: a diode hav ing its cathode connected to said grid; a resistance con nected between the anode of said diode and ground; a second capacitance across said resistance; said diode and said second capacitance cooperating with the diode consisting of the grid and cathode of said vacuum tube and said first capacitance to provide voltage doubling of said portion of the thus-modulated radiofrequency signal in said tank circuit; and means connected to the junction of said diode and said resistance for applying a signal of frequency Af to said detonatorfiring circuit. the amplitude of the Afsignal at said junc tion being approximately twice the amplitude of the Af signal at said grid. 

1. In a Doppler-type ordnance proximity fuze, said fuze having a tank circuit and means for causing radio-frequency energy of frequency fo to circulate in said tank circuit, said fuze also having antenna means for radiating radio-frequency energy of frequency fo from said tank circuit and for receiving a returned portion of said energy after reflection from a target, said returned portion as received by said antenna means having the frequency fo+ Delta f, the frequency shift Delta f being due to the relative motion of said fuze and said target, said returned portion having the effect of amplitude-modulating the radiofrequency energy in said tank circuit at a modulation frequency Delta f, said fuze also having rectifier means for the half-wave rectification of a portion of the thus-modulated radio-frequency signal in said tank circuit to obtain a rectified signal having a component of frequency Delta f, said fuze also having a detonator-firing circuit responsive to a component of frequency Delta f, the improvement comprising: a diode having its cathode connected to said rectifier means to receive said rectified signal; a resistance connected between the anode of said diode and ground; a capacitance across said resistance; said diode and said capacitance cooperating with said rectifier means to provide voltage doubling of said portion of the thus-modulated radiofrequency signal in said tank circuit; and means connected to the junction of said diode and said resistance for applying a signal of frequency Delta f to said detonator-firing circuit, the amplitude of the Delta f signal at said junction being approximately twice the amplitude of the Delta f signal at said rectifier means.
 2. In a Doppler-type ordnance proximity fuze, said fuze having a tank circuit and means comprising a vacuum tube for causing radio-frequency energy of frequency fo to circulate in said tank circuit, said vacuum tube having at least a plate and a grid and a cathode, said fuze also having antenna means for radiating radio-frequency energy of frequency fo from said tank circuit and for receiving a returned portion of said energy after reflection from a target, said returned portion as received by said antenna means having the frequency fo+ Delta f, the frequency shift Delta f being due to the relative motion of said fuze and said target, said returned portion having the effect of amplitude-modulating the radio-frequency signal in said tank circuit at a modulation frequency Delta f, a portion of the thus-modulated radio-frequency signal in said tank circuit being rectified by a circuit including the diode consisting of said grid and said cathode and a first capacitance to obtain at said grid a negative d-c voltage upon which is superimposed an a-c voltage of frequency Delta f, said fuze also having a detonator-firing circuit responsive to the frequency Delta f, the improvement comprising: a diode having its cathode conneCted to said grid; a resistance connected between the anode of said diode and ground; a second capacitance across said resistance; said diode and said second capacitance cooperating with the diode consisting of the grid and cathode of said vacuum tube and said first capacitance to provide voltage doubling of said portion of the thus-modulated radio-frequency signal in said tank circuit; and means connected to the junction of said diode and said resistance for applying a signal of frequency Delta f to said detonator-firing circuit, the amplitude of the Delta f signal at said junction being approximately twice the amplitude of the Delta f signal at said grid. 